Helicopter transmission mount system

ABSTRACT

A restraint system for a transmission in an aircraft can include a first strut having a first fluid chamber, a first piston resiliently coupled to a first housing with a first elastomeric member. The restraint system can include a second strut having second fluid chamber, a second piston resiliently coupled to a second housing with a second elastomeric member. The restraint system can include a fluid line between the first fluid chamber and the second fluid chamber. The first strut and the second strut collectively provide not only torque restraint, but also torque measurement and fore/aft vibration isolation.

BACKGROUND

1. Technical Field

The present disclosure relates to a helicopter transmission mountsystem.

2. Description of Related Art

Conventional transmission mount systems can utilize a plurality of legmounts for mounting the transmission to an airframe structure, such as aroof mounted pylon. Typically, the legs can have a single focal point orhave no focal point, both of which can act as a virtual center ofrotation. Creating a virtual center of rotation can increase the loadsfrom rolling or swinging of the transmission about the virtual center ofrotation. Such a conventional configuration lacks cross-coupling forstiffness and vibration reduction with load paths between multipledegrees of freedom.

Conventional transmission mount systems can utilize a plurality of legmounts for mounting the transmission to an airframe structure, such as aroof mounted pylon. However, conventional transmission mount systemslack the ability to not only attenuate vibration is certain directions,but also measure and resist certain loads, such as a torque load from arotor mast.

There is a need for an improved helicopter transmission mount system.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the embodiments of thepresent disclosure are set forth in the appended claims. However, theembodiments themselves, as well as a preferred mode of use, and furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a side view of a rotorcraft, according to an exampleembodiment;

FIG. 2 is perspective view of a transmission mount system for arotorcraft, according to an example embodiment;

FIG. 3 is a top plan view of a transmission mount system for arotorcraft, according to an example embodiment;

FIG. 4 is a side view of a transmission mount system for a rotorcraft,according to an example embodiment;

FIG. 5 is a front view of a transmission mount system for a rotorcraft,according to an example embodiment;

FIG. 6 is a bottom view of a transmission mount system for a rotorcraft,according to an example embodiment;

FIG. 7 is a perspective view of a transmission mount system for arotorcraft, according to an example embodiment;

FIG. 8 is a top plan view of a restraint system for a rotorcraft,according to an example embodiment;

FIG. 9 is a sectional schematic view of a restraint system for arotorcraft, according to an example embodiment; and

FIG. 10 is a sectional schematic view of a restraint system for arotorcraft, according to an example embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the embodiments are described below. In theinterest of clarity, all features of an actual implementation may not bedescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedeveloper's specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, apparatuses, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms such as “above,” “below,”“upper,” “lower,” or other like terms to describe a spatial relationshipbetween various components or to describe the spatial orientation ofaspects of such components should be understood to describe a relativerelationship between the components or a spatial orientation of aspectsof such components, respectively, as the device described herein may beoriented in any desired direction.

Referring now to FIG. 1 in the drawings, a rotorcraft 101 isillustrated. Rotorcraft 101 has a rotor system 103 with a plurality ofrotor blades 105. The pitch of each rotor blade 105 can be selectivelycontrolled in order to selectively control direction, thrust, and liftof rotorcraft 101. Rotorcraft 101 further includes a fuselage 107,anti-torque system 109, and an empennage 111. Rotorcraft 101 furtherincludes a landing gear system 113 to provide ground support for theaircraft. It should be appreciated that rotorcraft 101 is merelyillustrative of a variety of aircraft that can implement the embodimentsdisclosed herein. Other aircraft implementations can include hybridaircraft, tilt rotor aircraft, unmanned aircraft, gyrocopters, and avariety of helicopter configurations, to name a few examples. It shouldbe appreciated that even though aircraft are particularly well suited toimplement the embodiments of the present disclosure, non-aircraftvehicles and devices can also implement the embodiments.

Referring also to FIGS. 2-7 in the drawings, mount system 201 forsupporting a transmission 211 is illustrated in further detail. Mountsystem 201 can include a left forward leg 203 having a central axis 203a, a right forward leg 205 having a central axis 205 a, a left rear leg207 having a central axis 207 a, a right rear leg 209 having a centralaxis 209 a. Legs 203, 205, 207, and 209 can be structurally coupledbetween a structural pylon assembly 213 and lug mounts on transmission211, thereby providing the primary structural support of transmission211. The operationally induced forward, lateral, and torsional motionscan be reacted by a variety of arrangements; however, the preferredarrangement includes a left fore/aft strut 215 having a central axis 215a, a right fore/aft strut 217 having a central axis 217 a, and a lateralstrut 219 having a central axis 219 a.

One feature of mount system 201 is that left forward leg 203 and rightforward leg 205 are oriented such that axes 203 a and 205 a intersect ata forward focal point 221, while left rear leg 207 and right rear leg209 are oriented such that axes 207 a and 209 a intersect at an aftfocal point 223, the distance between forward focal point 221 and aftfocal point 223 forming a virtual roll axis 225 therebetween. In theillustrated embodiment, both forward focal point 221 and aft focal point223 lie on a centerline (e.g. zero buttline) of the rotorcraft 101.

One advantage of mount system 201 over conventional mount systems isthat by locating forward focal point 221 and aft focal point 223 ondifferent aircraft waterlines, the rolling tendency is substantiallydecreased. In the example embodiment, the waterline distance betweenforward focal point 221 and aft focal point 223 is represented by adistance D1, while the fuselage station difference between forward focalpoint 221 and aft focal point 223 is represented by a distance D2.

For example, transmission 211 can have a virtual swing arm S1 between acenter of gravity 227 and virtual roll axis 225 with which transmission221 will have a natural propensity to swing about. However, mount system201 is configured such that virtual roll axis 225 is substantiallyinclined by orienting aft focal point 223 with a substantially higherwaterline as compared to forward focal point 221, as illustrated bydistance D1. The inclination of virtual roll axis 225 impedes theswinging of transmission 221 which decreases the loads associated with aswinging of transmission 211.

In the example embodiment, each end of legs 203, 205, 207, and 209 arecoupled to the transmission 211 and pylon assembly 213 with sphericalbearings to prevent legs 203, 205, 207, and 209 from reacting loads inunintended directions. For example, fore/aft loads and torsional loadsare not reacted by legs 203, 205, 207, and 209, but rather by fore/aftstruts 215 and 217. Further, lateral loads are not reacted by legs 203,205, 207, and 209, but rather by lateral strut 219. Mounting legs 203,205, 207, and 209 with spherical bearings ensures that each leg 203,205, 207, and 209 will only react loads along its respective axis 203 a,205 a, 207 a, and 209 a. Further, prevention of load reaction outside ofaxis 203 a, 205 a, 207 a, and 209 a in combination with the freedom toadjust the waterline and fuselage station of forward focal point 221 andaft focal point 223 provides tunability to optimize vibration reductionand reduce rolling tendency of transmission about virtual roll axis 225.

It should be appreciated that if front legs 203 and 205, and aft legs207 and 209 were oriented so as to not have focal points, then mountsystem 201 would be very difficult to properly tune for vibrationattenuation and would likely require additional unique supportstructures, thereby increasing weight and vibration.

In one example embodiment, legs 203, 205, 207, and 209 are “soft” (i.e.not rigid) legs in that each leg 203, 205, 207, and 209 can includeinternal components, such as fluid, orifices, springs, elastomericmembers, and the like, to isolate and/or dampen vibrations between thetransmission 211 and the airframe of the aircraft. Similarly, struts215, 217, and 219 can include can include internal components, such asfluid, orifices, springs, elastomeric members, and the like, to isolateand/or dampen vibrations between the transmission 211 and the airframeof the aircraft. In one embodiment, legs 203, 205, 207, and 209 can beliquid inertia vibration elimination units described in U.S. Pat. No.6,431,530, issued on 13 Aug. 2002, which is hereby incorporated byreference, or described in U.S. Pat. No. 6,009,983, issued on 4 Jan.2000, which is also hereby incorporated by reference.

Referring now also to FIGS. 8-10, an example embodiment of a restraintsystem 801 is illustrated in further detail. Restraint system 801 is anembodiment of left fore/aft strut 215 and right fore/aft strut 217 thatcollectively provides not only torque restraint, but also torquemeasurement and fore/aft vibration isolation.

Restraint system 801 is particularly well suited to accompany a primarytransmission mount system, such as legs 203, 205, 207, 209 that areconfigured to not react fore/aft loads and torque loads, as discussedfurther herein. However, it should be appreciated that restraint system801 can accompany a transmission mount system having any plurality ofleg members oriented in a variety of different orientations.

Restraint system 801 includes a left fore/aft strut 215 having a piston803 resiliently coupled to a housing 805 with an elastomeric member 807.Piston 803 and elastomeric member 807 divide housing 805 into a firstchamber 809 and a second chamber 811. Similarly, restraint system 801includes a right fore/aft strut 217 having a piston 813 resilientlycoupled to a housing 815 with an elastomeric member 817. Piston 813 andelastomeric member 817 divide housing 815 into a first chamber 819 and asecond chamber 821.

Second chamber 811, second chamber 821, and a fluid line 823 are filledwith a fluid 829. First chamber 809 and first chamber 819 don't requirefluid 829 and thus can be open or vented rather than being enclosedchambers. For example, first chamber 809 and first chamber 819 can befilled with air, or open/vented to atmosphere.

During operation, restraint system 801 is configured to resist/reacttorque loads, measure torque loads, as well as attenuate vibration inthe fore/aft direction. Referring in particular to FIG. 9, restraintsystem 801 is illustrated with regard to the reaction and measurement oftorque loads. During operation of a rotorcraft, such as rotorcraft 101,torque is carried in the rotor mast and into transmission 211. Variousmaneuvers and operations of the rotorcraft 101 can cause the amount oftorque to vary significantly. For example, an increase in rotor bladepitch during a hover maneuver can increase the amount of torque loadupon transmission 211. One of ordinarily skill in the art wouldappreciate that the tail rotor 109 acts to provide anti-torque tocounter the torque reacted by transmission 211 and provide for yawcontrol.

As discussed further herein, legs 203, 205, 207, and 209 are configuredto not react torque, thus the torque experienced by transmission 211 isreacted by fore/aft struts 217 and 219. Preferably, fore/aft struts 217and 219 are mounted with spherical bearings so that the torque load issubstantially realized as a forward directional load 831 along axis 217a and aft direction load 833 along axis 215 a. Forward directional load831 attempts to pull piston 813 forward, but the equal and opposite aftdirectional load 833 attempts to push piston 803, thereby creating anfluid lock since the fluid 829 in second chamber 811 is in fluidcommunication with the fluid 829 in first fluid chamber 819 via fluidline 823. As such, the torque is restrained with a stiffness that isdependent upon the bulk modulus (or stiffness) of the implementationspecific fluid 829. Furthermore, the amount of torque reacted byfore/aft struts 217 and 219 can be measured by a pressure sensor 825.Pressure sensor 825 can be in communication with one or more processorsfor analysis. In another embodiment, pressure sensor 825 is incommunication with a visual gauge in the cockpit of the aircraft so thatthe operator can evaluate the torque in real time.

It should be appreciated that the direction of forward directional load831 and aft direction load 833 can be directionally reversed in the caseof a rotorcraft having a main rotor hub that turns in the oppositedirection from that of the example embodiment.

Referring now also to FIG. 10, restraint system 801 is illustrated withregard to the attenuation of oscillatory vibration in the fore/aftdirection. Oscillatory vibration loads can be generated duringoperation, some of the oscillatory vibrations can have a fore/aftcomponent. In FIG. 10, an oscillatory load left untreated would berealized as a vibration in the aircraft. For illustrative purposes, theoscillatory load is schematically shown in an aft direction by directionarrows 835; however, it should be appreciated that the load oscillatesfore/aft at a certain frequency. When the load is in the aft direction,shown by arrows 835, pistons 803 and 813 are pushed aft, which decreasesthe volume of fluid 829 in second chamber 811 and increases the volumeof fluid 829 in first chamber 819, thereby creating a net shift in fluidin a forward direction. The axial shift in fluid 829 acts to cancel theload input in that the mass of the fluid 829 shift creates an inertialmass cancellation of the input. Since the fore/aft load oscillatesfore/aft at a certain frequency, the restraint system 801 employs theprinciple that the acceleration of an oscillating mass is 180° out ofphase with its displacement.

Utilizing a fluid 829 with high density and low viscosity provides thedesired inertial characteristics, combined with a hydraulic advantageresulting from a piston arrangement, so as to harness the out-of-phaseacceleration to generate counter balancing forces to attenuate or cancelthe vibration. During operation, elastomeric members 807 and 817 act asspring members. The fluid line 823 acts as an inertia track and can betuned so that the restraint system 801 attenuates vibration at a desiredfrequency. Further, if the fore/aft oscillatory load varies, then anoptional active pumper 827 can be utilized to actively adjust theisolation frequency by imparting pumping fluid 829 at a frequency thatadjusts the isolation frequency.

A vibration isolator that operates under a similar principle isdescribed in U.S. Patent Application Publication 2013/0175389, filed on10 Jan. 2012, which is hereby incorporated by reference.

One advantage of restraint system 801 is that that it uniquely not onlyattenuates vibration in certain directions, but also measures andresists certain loads, such as a torque load from a rotor mast.

The particular embodiments disclosed above are illustrative only, as theapparatus may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Modifications, additions, or omissions may be made tothe apparatuses described herein without departing from the scope of theinvention. The components of the apparatus may be integrated orseparated. Moreover, the operations of the apparatus may be performed bymore, fewer, or other components.

Furthermore, no limitations are intended to the details of constructionor design herein shown, other than as described in the claims below. Itis therefore evident that the particular embodiments disclosed above maybe altered or modified and all such variations are considered within thescope and spirit of the application. Accordingly, the protection soughtherein is as set forth in the claims below.

To aid the Patent Office, and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims to invokeparagraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereofunless the words “means for” or “step for” are explicitly used in theparticular claim.

1. A restraint system for a transmission in an aircraft, the restraintsystem comprising: a first strut having a first piston resilientlycoupled to a first housing with a first elastomeric member, wherein thefirst housing, the first piston, and the first elastomeric member form afirst fluid chamber; a second strut having a second piston resilientlycoupled to a second housing with a second elastomeric member, whereinthe second housing, the second piston, and the second elastomeric memberform a second fluid chamber; a fluid line placing the first fluidchamber and the second fluid chamber in fluid communication; a fluid inthe first fluid chamber, the second fluid chamber, and the fluid line;wherein an actuation of the first piston and the second piston in afirst direction causes a portion of the fluid to move into one of thefirst fluid chamber and the second fluid chamber.
 3. The restraintsystem according to claim 1, wherein a first load on the first piston ina first direction, and a second load on the second piston in an oppositedirection from the first direction causes a fluid lock.
 4. The restraintsystem according to claim 3, wherein the fluid lock acts to prevent thefirst piston from translating relative to the first housing.
 5. Therestraint system according to claim 3, wherein the fluid lock acts toprevent the second piston from translating relative to the secondhousing.
 6. The restraint system according to claim 1, wherein the firststrut is oriented parallel to the second strut.
 7. The restraint systemaccording to claim 1, wherein the first piston and the second piston arecoupled to an airframe of the aircraft.
 8. The restraint systemaccording to claim 1, wherein the first housing and the second housingare coupled to the transmission.
 9. The restraint system according toclaim 1, wherein the first piston and the second piston are orientedparallel to a longitudinal axis of the aircraft.
 10. The restraintsystem according to claim 1, further comprising: a pressure sensorconfigured to measure a pressure of the fluid.
 11. The restraint systemaccording to claim 10, wherein the pressure sensor is configured toprovide a measurement of torque experienced by the transmission.
 12. Therestraint system according to claim 1, wherein the aircraft is ahelicopter.
 13. The restraint system according to claim 1, wherein thetransmission is coupled to a main rotor mast of a rotor hub.
 14. Therestraint system according to claim 1, wherein the portion of fluid thatmoves into one of the first fluid chamber and the second fluid chamberhas an inertial mass that cancels a force that actuates the first pistonand the second piston.
 15. A restraint system for a transmission in anaircraft, the restraint system comprising: a first strut having a firstpiston resiliently coupled to a first housing with a first elastomericmember, wherein the first housing, the first piston, and the firstelastomeric member form a first fluid chamber; a second strut having asecond piston resiliently coupled to a second housing with a secondelastomeric member, wherein the second housing, the second piston, andthe second elastomeric member form a second fluid chamber; a fluid linebetween the first fluid chamber and the second fluid chamber; and afluid in the first fluid chamber, the second fluid chamber, and thefluid line; wherein a first load on the first piston in a firstdirection, and a second load on the second piston in an oppositedirection from the first direction, causes a fluid lock.
 16. Therestraint system according to claim 15, wherein the fluid lock causesthe first strut and the second strut to behave rigidly.
 17. Therestraint system according to claim 15, wherein the first load and thesecond load are generated from a torque load on the transmission. 18.The restraint system according to claim 15, further comprising: apressure sensor configured to measure a fluid pressure of the fluid. 19.The restraint system according to claim 15, wherein the first piston andthe second piston are coupled to an airframe of the aircraft.
 20. Therestraint system according to claim 15, wherein the first housing andthe second housing are coupled to the transmission.